Rs4862705 in the melatonin receptor 1A gene is associated with renal function decline in type 1 diabetes individuals.

Aim: The pathogenesis of chronic diabetes complications has oxidative stress as one of the major elements, and single-nucleotide polymorphisms (SNPs) in genes belonging to antioxidant pathways modulate susceptibility to these complications. Considering that melatonin is a powerful antioxidant compound, our aim was to explore, in a longitudinal cohort study of type 1 diabetes (T1D) individuals, the association of microvascular complications and SNPs in the gene encoding melatonin receptor 1A (MTNR1A). Methods: Eight SNPs in MTNR1A were genotyped in 489 T1D individuals. Besides cross-sectional analyses of SNPs with each one of the microvascular complications (distal polyneuropathy, cardiovascular autonomic neuropathy, retinopathy, and diabetic kidney disease), a longitudinal analysis evaluated the associations of SNPs with renal function decline in 411 individuals followed up for a median of 8 years. In a subgroup of participants, the association of complications with urinary 6-sulfatoxymelatonin (aMT6s) concentration was investigated. Results: The group of individuals with a renal function decline ≥ 5 mL min-1 1.73 m-2 year-1 presented a higher frequency of the A allele of rs4862705 in comparison with nondecliners, even after adjustment for confounding variables (OR = 1.84, 95% CI = 1.20-2.82; p = 0.0046). No other significant associations were found. Conclusions: This is the first study showing an association between a variant in a gene belonging to the melatonin system and renal function decline in the diabetic setting.

Variant rs17619600 in the gene encoding serotonin receptor 2B (HTR2B) increases the risk of gestational diabetes mellitus: a case-control study.

BACKGROUND: During pregnancy, the increase in maternal insulin resistance is compensated by hyperplasia and increased function of maternal pancreatic beta cells; the failure of this compensatory mechanism is associated with gestational diabetes mellitus (GDM). Serotonin participates in beta cell adaptation, acting downstream of the prolactin pathway; the blocking of serotonin receptor B (HTR2B) signaling in pregnant mice impaired beta cell expansion and caused glucose intolerance. Thus, given the importance of the serotoninergic system for the adaptation of beta cells to the increased insulin demand during pregnancy, we hypothesized that genetic variants (single nucleotide polymorphisms [SNPs]) in the gene encoding HTR2B could influence the risk of developing GDM. METHODS: This was a case-control study. Five SNPs (rs4973377, rs765458, rs10187149, rs10194776, and s17619600) in HTR2B were genotyped by real-time polymerase chain reaction in 453 women with GDM and in 443 pregnant women without GDM. RESULTS: Only the minor allele C of SNP rs17619600 conferred an increased risk for GDM in the codominant model (odds ratio [OR] 2.15; 95% confidence interval [CI] 1.53-3.09; P < 0.0001) and in the rare dominant model (OR 2.32; CI 1.61-3.37; P < 0.0001). No associations were found between the SNPs and insulin use, maternal weight gain, newborn weight, or the result of postpartum oral glucose tolerance test (OGTT). In the overall population, carriers of the XC genotype (rare dominant model) presented a higher area under the curve (AUC) of plasma glucose during the OGTT, performed for diagnostic purposes, compared with carriers of the TT genotype of rs17619600. CONCLUSIONS: SNP rs17619600 in the HTR2B gene influences glucose homeostasis, probably affecting insulin release, and the presence of the minor allele C was associated with a higher risk of GDM.

Identification of two patterns of mitochondrial DNA-copy number variation in postcentral gyrus during aging, influenced by body mass index and type 2 diabetes.

AIMS: Mitochondrial (mt) DNA replication is strongly associated with oxidative stress, a condition triggered by aging and hyperglycemia, both of which contribute to mitophagy disruption and inflammation. This observational exploratory study evaluated mtDNA-copy number (mtDNA-CN) and expression of genes involved in mitochondriogenesis (PPARGC1A, TFAM, TFB1M, TFB2M), mitophagy (PINK1, PRKN), and inflammatory pathways triggered by hyperglycemia (TXNIP, NLRP3, NFKB1), in the postcentral gyrus of adults and older individuals with and without type 2 diabetes mellitus (T2D). MAIN METHODS: Quantitative real-time PCR was employed to evaluate mtDNA-CN and gene expression; tissue autofluorescence, a marker of aging and of cells with damaged organelles, was also quantified. KEY FINDINGS: No correlation was found between age and mtDNA-CN, but a direct correlation was observed for cases with mtDNA-CN >1000 (r = 0.41). The mtDNA-CN >1000 group had greater tissue autofluorescence and higher body mass index compared to the mtDNA-CN <1000 group (BMI; 25.7 vs 22.0 kg/m2, respectively). mtDNA-CN correlated with tissue autofluorescence in the overall sample (r = 0.55) and in the T2D group (r = 0.64). PINK and PRKN expressions were inversely correlated with age. Mitochondriogenesis genes and TXNIP expressions were higher in the T2D group, and correlations among the mitochondriogenesis genes were also stronger in this group, relative to the subgroup with mtDNA-CN >1000.

Variants in HSD11B1 gene modulate susceptibility to diabetes kidney disease and to insulin resistance in type 1 diabetes.

BACKGROUND AND AIM: 11ß-Hydroxysteroid dehydrogenase 1 has been implicated in insulin resistance (IR) in the setting of metabolic disorders, and single nucleotide polymorphisms (SNPs) in its encoding gene (HSD11B1) have been associated with type 2 diabetes and metabolic syndrome. In type 1 diabetes (T1D), IR has been related to the development of chronic complications. We investigated the association of HSD11B1 SNPs with microvascular complications and with IR in a Brazilian cohort of T1D individuals. MATERIALS AND METHODS: Five SNPs were genotyped in 466 T1D individuals (57% women; median of 37 years old, diabetes duration of 25 years and HbA1c of 8.4%). RESULTS: The minor allele T of rs11799643 was nominally associated with diabetic retinopathy (OR = 0.52; confidence interval [CI] 95% = 0.28-0.96; P = .036). The minor allele C of rs17389016 was nominally associated with overt diabetic kidney disease (DKD) (OR = 1.90; CI 95% = 1.07-3.37; P = .028). A follow-up study revealed that 29% of the individuals lost ≥5 mL min-1 × 1.73 m2 per year of the estimated glomerular filtration rate (eGFR). In these individuals (eGFR decliners), C allele of rs17389016 was more frequent than in non-decliners (OR = 2.10; CI 95% = 1.14-3.89; P = .018). Finally, minor allele T of rs846906 associated with higher prevalence of arterial hypertension, higher body mass index and waist circumference, thus conferring risk to a lower estimated glucose disposal rate, a surrogate marker of insulin sensitivity (OR = 1.23; CI 95% = 1.06-1.42; P = .004). CONCLUSION: SNPs in the HSD11B1 gene may confer susceptibility to DKD and to IR in T1D individuals.

Increased leukotriene B4 plasma concentration in type 2 diabetes individuals with cardiovascular autonomic neuropathy.

BACKGROUND AND AIM: A low-grade inflammation is associated with cardiac autonomic neuropathy (CAN) and increased concentration of leukotriene B4 (LTB4) was found in individuals with type 1 diabetes and definitive CAN. This cross-sectional study evaluated plasma concentration of LTB4 and of other inflammatory mediators, namely, tumor necrosis factor (TNF), interleukin (IL)1B, and IL10 in individuals with type 2 diabetes (T2D) and different degrees of CAN, and correlated these inflammatory mediators with the degree of glycemic control and with a surrogate marker of insulin resistance. METHODS: TNF, IL1B, IL10 and LTB4 plasma concentrations were measured in 129 T2D subjects (62% women with [median] age of 63 years, disease duration of 8 years and HbA1c of 7.3%) with or without CAN. The Lipid accumulation product index was used as a surrogate marker of insulin resistance. RESULTS: LTB4 concentration was significantly higher in those presenting incipient CAN (69.7 ± 16.6 pg mL-1) and definitive CAN (71.5 ± 15.7 pg mL-1) versus those without CAN (57.0 ± 13.9 pg mL-1). The groups without CAN and with incipient CAN were pooled (group without definitive CAN) and compared to those with definitive CAN. LTB4 concentration was higher in the latter group, as well as TNF concentration, while IL10 concentration was lower in this group. After adjustment for confounding variables, only LTB4 concentration remained significantly different between the groups with and without definitive CAN. Plasma concentration of LTB4 did not correlate with the degree of glycemic control. After sorting the participants by sex, a borderline weak correlation was found between LTB4 and the Lipid accumulation product index in women. CONCLUSION: In the T2D setting, circulating LTB4 concentration seems to be associated with cardiovascular dysautonomia.

Distal Symmetric and Cardiovascular Autonomic Neuropathies in Brazilian Individuals with Type 2 Diabetes Followed in a Primary Health Care Unit: A Cross-Sectional Study.

The paucity of epidemiological data regarding diabetes complications in Brazil motivated us to evaluate the prevalence rates of distal symmetric polyneuropathy (DSP) and of cardiovascular autonomic neuropathy (CAN) in individuals with type 2 diabetes (T2D) followed in a primary care unit. A total of 551 individuals (59.3% women, 65 years old; diabetes duration of 10 years; HbA1c of 7.2%, medians) were included in this cross-sectional study. DSP was diagnosed by sum of the Neuropathy Symptoms Score (NSS) and Modified Neuropathy Disability Score (NDS) and by the Semmes-Weinstein monofilament. CAN was diagnosed by cardiovascular autonomic reflex tests combined with spectral analysis of heart rate variability. The prevalence rates of DSP were 6.3% and 14.3%, as evaluated by the sum of NSS and NDS and by the Semmes-Weinstein monofilament, respectively. Those with DSP diagnosed by monofilament presented longer diabetes duration, worse glycemic control and a higher stature. The prevalence rates of incipient and definitive CAN were 12.5% and 10%, respectively. Individuals with definitive CAN presented a higher frequency of hypercholesterolemia and of arterial hypertension. The higher prevalence rate of DSP with the use of the monofilament suggests that it may be a more appropriate tool to diagnose DSP in the primary care setting in Brazil.

Allelic variations in genes belonging to glutathione system increase proliferative retinopathy risk in type 1 diabetes individuals.

AIMS: Given the participation of oxidative stress in the pathogenesis of diabetic complications, we evaluated, in type 1 diabetes (T1D) individuals, the association between diabetic retinopathy (DR) and functional single nucleotide polymorphisms (SNPs) in regulatory regions of two genes belonging to the antioxidant glutathione (GSH) system: rs17883901 in GCLC and rs713041 in GPX4. METHODS: A cross-sectional case-control study included 288 individuals (61% women, 34[±11] years old, diabetes duration of 22[±9] years, mean [±SD]) sorted according to DR stages: absence of DR (ADR), non-proliferative DR (NPDR) and proliferative DR (PDR). SNPs were genotyped by real-time PCR using fluorescent labelled probes. Logistic regression models with adjustment for confounding covariates were employed. RESULTS: The presence of at least one T-allele of rs17883901 in GCLC was an independent risk factor for PDR (OR 4.13, 95% CI 1.38-13.66, p = 0.014) in a polytomous regression model (PDR versus ADR). The presence of at least one T-allele of rs713041 in GPX4 conferred protection against PDR (OR 0.30, 95% CI 0.11-0.80, p = 0.017) in female T1D individuals. CONCLUSION: The functional SNPs rs17883901 and rs713041 modulate the risk for PDR in the studied population of T1D individuals, widening the spectrum of candidate genes for this complication.

Glutathione peroxidase 4 functional variant rs713041 modulates the risk for cardiovascular autonomic neuropathy in individuals with type 1 diabetes.

Cardiac autonomic neuropathy is a neglected diabetic chronic complication for which genetic predictors are rarely reported. Oxidative stress is implicated in the pathogenesis of microvascular complications, and glutathione peroxidase 4 is involved in the detoxification of peroxides and of reactive oxygen species. Thus, the association of a functional variant in the gene encoding glutathione peroxidase 4 (rs713041) with this diabetic complication was investigated in 341 individuals with type 1 diabetes evaluated for cardiac autonomic neuropathy status (61.7% women, 34 [27-42] years old; diabetes duration: 21 [15-27] years; HbA1c: 8.3% [7.4-9.4]; as median [interquartile interval]). Cardiac autonomic neuropathy was present in 29% of the participants. There was an inverse association of the minor T allele of rs713041 with cardiac autonomic neuropathy (odds ratio = 0.39; 95% confidence interval = 0.17-0.90; p = 0.0271) after adjustment for potential confounders. The functional glutathione peroxidase 4 variant rs713041 modulated the risk for cardiac autonomic neuropathy in the studied population with type 1 diabetes.

Genetic variants in DNMT1 and the risk of cardiac autonomic neuropathy in women with type 1 diabetes.

AIMS/INTRODUCTION: Epigenetics participate in the pathogenesis of metabolic memory, a situation in which hyperglycemia exerts prolonged deleterious effects even after its normalization. We tested the hypothesis that genetic variants in an epigenetic gene could predispose to diabetes complications. MATERIAL AND METHODS: We assessed the frequency of five single-nucleotide polymorphisms in the gene encoding deoxyribonucleic acid methytransferase 1 (DNMT1; rs8112895, rs7254567, rs11085721, rs17291414 and rs10854076), and their associations with diabetic kidney disease, retinopathy, distal polyneuropathy and autonomic cardiovascular neuropathy in 359 individuals with long-term type 1 diabetes. RESULTS: None of the single-nucleotide polymorphisms studied was significantly associated with the presence of chronic complications in the overall population. However, after sex stratification, the minor allele C of rs11085721 conferred risk for cardiovascular neuropathy in women after adjustment for confounding variables (odds ratio 2.32; 95% confidence interval 1.26-4.33; P = 0.006). CONCLUSIONS: The fact that heterozygous mutations in DNMT1 are associated with hereditary sensory autonomic neuropathy provides plausibility to the present finding. If confirmed in independent samples, it suggests that genetic variants in epigenetic genes might predispose to more or fewer epigenetic changes in the face of similar metabolic derangements triggered by hyperglycemia, constituting the "genetics of epigenetics" for microvascular diabetes complications.

N-Acetyl Cysteine Attenuated the Deleterious Effects of Advanced Glycation End-Products on the Kidney of Non-Diabetic Rats.

AIM: To assess the renal effects of chronic exposure to advanced glycation end-products (AGEs) in the absence of diabetes and the potential impact of concomitant treatment with the antioxidant N-acetyl cysteine (NAC). METHODS: Wistar rats received intraperitoneally 20 mg/kg/day of albumin modified (AlbAGE) or not (AlbC) by advanced glycation for 12 weeks and oral NAC (600mg/L; AlbAGE+NAC and AlbC+NAC, respectively). Biochemical, urinary and renal morphological analyses; carboxymethyl-lysine (CML, an AGE), CD68 (macrophage infiltration), and 4-hydroxynonenal (4-HNE, marker of oxidative stress) immunostaining; intrarenal mRNA expression of genes belonging to pathways related to AGEs (Ager, Ddost, Nfkb1), renin-angiotensin system (Agt, Ren, Ace), fibrosis (Tgfb1, Col4a1), oxidative stress (Nox4, Txnip), and apoptosis (Bax, Bcl2); and reactive oxidative species (ROS) content were performed. RESULTS: AlbAGE significantly increased urine protein-to-creatinine ratio; glomerular area; renal CML content and macrophage infiltration; expression of Ager, Nfkb1, Agt, Ren, Tgfb1, Col4a1, Txnip, Bax/Bcl2 ratio; and 4-HNE and ROS contents. Some of these effects were attenuated by NAC concomitant treatment. CONCLUSION: Because AGEs are highly consumed in modern diets and implicated in the progression of different kidney diseases, NAC could be a therapeutic intervention to decrease renal damage, considering that long-term restriction of dietary AGEs is difficult to achieve in practice.

Optimization of total RNA isolation from human urinary sediment.

Extracting RNA from human urinary sediment is notoriously challenging because of cell paucity and hostile environment and column-based commercial kits using silica technology are commonly used. Nonetheless, in our experience, this methodology yields low amounts of total RNA and has low rates of success. We replaced the column-based commercial kit by a protocol using guanidine isothiocyanate-phenol-chloroform buffer (Trizol reagent) followed by addition of glycogen as a carrier and precipitation with isopropanol plus sodium acetate. This methodology was more affordable and efficient for urinary sediment total RNA isolation than silica technology, resulting in higher concentrations of total RNA of better quality.

Beta-2-microglobulin (B2M) expression in the urinary sediment correlates with clinical markers of kidney disease in patients with type 1 diabetes.

PURPOSE: After observing variation in the expression of the housekeeping gene B2M in cells of the urinary sediment during a study of candidate genes potentially involved in diabetic kidney disease (DKD), we hypothesized that B2M mRNA expression in the urinary sediment could reflect the presence of DKD. METHODS: qPCR was used to quantify B2M mRNA expression in cells of the urinary sediment of 51 type 1 diabetes (T1D) patients (61% women, 33.5 [27.0-39.7] years old, with diabetes duration of 21.0 [15.0-28.0] years and HbA1c of 8.2% [7.3-8.9]; median [interquartile interval]) sorted according to the diabetic nephropathy (DN) stages; 8 focal segmental glomerulosclerosis (FSGS) patients and 10 healthy controls. B2M mRNA expression was also evaluated in human embryonic kidney epithelium-like (HEK-293) cells exposed to 25mM glucose and to albumin in order to mimic, respectively, a diabetic and a proteinuric milieu. RESULTS: No differences were found in B2M mRNA expression among healthy controls, FSGS and T1D patients. Nonetheless B2M mRNA expression was higher in the group composed by T1D patients with incipient or overt DN combined with FSGS patients versus T1D patients without DN combined with healthy controls (P=0.0007). B2M mRNA expression was higher in T1D patients with incipient or overt DN versus without DN (P=0.03). B2M mRNA expression positively correlated with albuminuria in the overall T1D population (r=0.43; P=0.01) and negatively correlated with estimated glomerular filtration rate in male T1D patients (r=- 0.57; P=0.01). Increased B2M expression was observed in HEK-293 cells exposed to 25mM glucose and to albumin. CONCLUSIONS: Β2M mRNA expression in cells of the urinary sediment is higher in T1D patients with DKD and in patients with FSGS in comparison to healthy subjects, maybe reflecting a tubulointerstitial injury promoted by albumin. Given the proinflammatory nature of B2M, we suggest that this protein contributes to diabetic (and possibly, to non-diabetic) tubulopathy.

Thioredoxin interacting protein expression in the urinary sediment associates with renal function decline in type 1 diabetes.

AIMS: Thioredoxin interacting protein (TXNIP), an inhibitor of antioxidant thioredoxin (Trx), is upregulated by hyperglycemia and implicated in pathogenesis of diabetes complications. We evaluated mRNA expressions of genes encoding TXNIP and Trx (TXN) in urinary sediment and peripheral blood mononuclear cells (PBMC) of type 1 diabetes (T1D) patients with different degrees of chronic complications. METHODS: qPCR was employed to quantify target genes in urinary sediment (n = 55) and PBMC (n = 161) from patients sorted by presence or absence of diabetic nephropathy (DN), retinopathy, peripheral and cardiovascular neuropathy; 26 healthy controls and 13 patients presenting non-diabetic nephropathy (focal and segmental glomerulosclerosis, FSGS) were also included. RESULTS: Regarding the urinary sediment, TXNIP (but not TXN) expression was higher in T1D (p = 0.0023) and FSGS (p = 0.0027) patients versus controls. Expressions of TXNIP and TXN were higher, respectively, in T1D patients with versus without DN (p = 0.032) and in those with estimated glomerular filtration rate (eGFR) < 60 versus ≥60 mL/min/1.73 m(2) (p = 0.008). eGFR negatively correlated with TXNIP (p = 0.04, r = -0.28) and TXN (p = 0.04, r = -0.30) expressions. T1D patients who lost ≥5 mL/min/1.73 m(2) yearly of eGFR presented higher basal TXNIP expression than those who lost <5 mL/min/1.73 m(2) yearly after median follow-up of 24 months. TXNIP (p < 0.0001) and TXN (p = 0.002) expressions in PBMC of T1D patients were significantly higher than in controls but no differences were observed between patients with or without chronic complications. CONCLUSIONS: TXNIP and TXN are upregulated in urinary sediment of T1D patients with diabetic kidney disease (DKD), but only TXNIP expression is associated with magnitude of eGFR decline.